The present invention relates generally to signal acquisition and, more particularly, to correction of a non-linear signal.
Various electronic sensors, data acquisition systems and other electronic systems using a bandgap reference for data correction are used in a variety of applications, such as for acquiring information in manufacturing, testing, analysis and other experimental and industrial applications. In these and other applications, obtaining accurate data is important.
Particular applications for which data collection is important include sensing various characteristics, such as temperature, pressure and others. In many applications, a bandgap voltage reference forms an essential part of a sensor. The voltage reference provides the reference signal that is used to convert the sensor""s characteristic dependent voltage into the digital domain. Given the availability of an accurate signal in the form of a voltage, the overall accuracy of a sensor is determined by the accuracy of the bandgap reference.
For example, many conventional bandgap references show a non-linear dependence, or curvature. This curvature causes a non-linear error in the output of a sensor based on such a bandgap reference. Many methods have been used to correct the curvature of a bandgap reference circuit, though not necessarily in the context of a sensor. Example categories of such methods include methods that change the bias current of the bipolar transistors in the reference and methods that generate a non-linear correction signal that is added to the output of the original reference; e.g. a piece-wise linear correction, an exponential correction, or a quadratic correction.
In these and other methods, cancellation of higher-order terms is not possible. In addition, many cancellation methods are limited in use to specific applications. These challenges inhibit the ability to obtain an accurate signal in a variety of applications.
The present invention is directed to the correction of a non-linear signal in various applications. The present invention is exemplified in a number of implementations and applications, some of which are summarized below.
According to an example embodiment of the present invention, a non-linear output signal from a bipolar transistor circuit having a base-emitter voltage is corrected. A corrected output corresponding to the detectable characteristic is determined as a function of the base-emitter voltage, the non-linear output signal and a generated non-linear signal. The generated non-linear signal is adapted to cancel the non-linearity of the non-linear output signal when added thereto, and improves the ability to obtain an accurate signal that is free from non-linear output that results from third and higher-order components.
According to another example embodiment of the present invention, a system is adapted for correcting a non-linear output signal from a bipolar transistor circuit having a base-emitter voltage, wherein the non-linear output signal corresponds to a detectable characteristic, such as temperature, pressure or other characteristic. The system includes a signal generation arrangement adapted to generate a non-linear signal. The generated non-linear signal is adapted to cancel the non-linearity of the non-linear output signal when added thereto. A correction circuit is adapted to provide a corrected output corresponding to the detectable characteristic and to determine a corrected output as a function of the base-emitter voltage, the non-linear output signal and the generated non-linear signal.
The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and detailed description that follow more particularly exemplify these embodiments.